Large machines may require a lot of braking power in order to slow down and stop, or to maintain ground speed with descending grades. As such, many large machines are equipped with at least two types of braking systems. In some instances, both a typical friction brake system is used as well as a retarder system. Typical retarder systems (sometimes referred to as engine brakes) may use the engine to slow down the machine. Retarder systems may work very well in slowing a machine down. However, some retarder system's effectiveness decreases as the machine speed becomes low. Therefore, it is difficult for some retarder systems to bring a machine to a complete stop. This is where the friction brake system is useful, in that it can stop a machine. However, one problem with friction brake systems is they can overheat and ware with overuse. Even machines with wet brake systems, where the rotor and the stator associated with the brake system may be immersed in oil, may have the friction brake systems and the associated oil overheat if the friction brake systems are overused.
U.S. Pat. No. 8,491,064 describes a method for braking a machine. According to this patent, the machine includes a circuit adapted for transmitting a brake signal from an operator control braking element to brake devices arranged at a plurality of the machine's ground engaging elements via a brake fluid. The method includes detecting a fluid pressure in the circuit, using the detected fluid pressure level as an input for determining a brake power for at least one auxiliary brake in the machine and controlling the auxiliary brake responsively.
However, for various reasons it may be desirable to operate an auxiliary braking systems such as a retarder system using different inputs other than fluid pressure.
Accordingly, it is desirable to provide a method and apparatus that can detect an operator's call for braking power and operate appropriate braking systems in order to slow the machine in accordance with the operator's call for braking power.